Liquids such as drug solutions are conventionally supplied to patients using a transfusion line provided with a tube. In such cases, it is difficult to visually confirm the flow of the liquid if there is a small amount of liquid to be administered to the patient. Furthermore, even if a liquid flow detector for detecting the flow of liquid is incorporated into the transfusion line, this liquid flow detector must be such that it does not obstruct administration of the liquid to the patient. In addition, there may be cases where the liquid flow detector is used only once, and an inexpensive liquid flow detector which does not utilize a device such as an electrical sensor or an optical sensor is required in such cases. There are instruments such as this in which a spherical body which moves along with the flow of liquid is provided in the liquid flow detector.
This liquid flow detector (flowmeter) has a configuration in which an inlet port extending horizontally and a conical upper flow channel extending vertically are connected by a narrow passage, and a spherical body is arranged inside the upper flow channel. The upper flow channel is formed so that the upper part has a somewhat larger diameter than the lower part, and the flow of the liquid can be detected by the position of the spherical body which moves inside the upper flow channel depending on the flow of liquid, which also allows the flow rate of the liquid to be measured.
However, with the conventional liquid flow detector described above, it is difficult to detect the flow of liquid if the liquid to be administered to the patient is in an extremely small amount, for example if the flow velocity is of the order of 1 ml per hour.
The present invention has been devised in view of the situation outlined above, and it aims to provide an inexpensive liquid flow detector which can detect the flow of a minute amount of liquid, and a transfusion line provided with same.